Conventionally, in a metal gasket formed by superposing a plurality of metal plates, as shown in FIG. 19, the plurality of metal plates are connected in a laminating direction by forming a connecting portion 41 of a tongue shape at an outer peripheral edge outside a joining surface between a cylinder block and a cylinder head, and by forming an eyelet hole 5 by forming a through hole in the connecting portion 41, inserting a metal fitting for locking through the hole, and by collapsing the metal fitting, and alternatively, the metal plates are welded at this connecting portion 41.
However, the method by means of the eyelet hole requires labour hours for connecting work, and the method by the welding requires facility cost although the labour hours are reduced. Thus, a method for making the connecting work easy is required.
In this respect, Japanese Patent Laid Open Publication Hei No. 6-281011 discloses a method for connecting a metal gasket by a press work. In this method, as shown in FIGS. 20 to 22, a plurality of cutting lines 30a independent of one another are formed in laminated metal plates, and at the same time, a projecting portion 30b is formed by protruding a metal plate portion between the cutting lines 30a by a height larger than a thickness of the laminated metal plates in a laminating direction, and furthermore, a burr is formed at the cut end portion by making a break line by extending a portion 30c of the cutting line 30a.
In this method, the displacement or slippage of the laminated metal plates in the plate plane in a direction intersecting an extending direction of the cutting line is prevented by collision, at opposite ends of the cutting line, between a cut end face of the laminated metal plate portion not protruded and an end face of the protruded portion, and the slippage or displacement of the laminated metal plates in the laminating direction is prevented by spring back of the burr.
However, in the connecting structure described in the above-mentioned Japanese Patent Laid Open Publication Hei No. 6-281011 as shown in FIGS. 20 to 22, it is described that when viewed in the laminating direction, the tip end portions of the burrs overlap with each other and the overlapped portions serve as the slippage or displacement preventing means, however, in practice, the slippage or displacement preventing effect was not sufficient. Furthermore, in order to prevent the displacement in every direction in the plate plane of the laminated metal plates, it is necessary to form three or more cutting lines as shown in FIG. 20 or 21, and a problem is involved in which a mold used to form such a connecting structure has a complicated structure, and it is easily broken and the cost is high.
The present invention was made in view of the problems in the prior art as mentioned above, and it is a subject to provide a method which prevents the slippage or displacement of the metal plates in the laminating direction, and which prevents the displacement of the laminated metal plates in every direction in the plate plane without making a mold shape complicated, and still, can be done by press forming of one time, and to provide a press mold used for the method.